One of the major problems of interest in defending against chemical warfare is the detection of chemical agent contamination of the atmosphere. This problem has existed since chemical warfare was first used.
To this end the U.S. Army has developed a portable Fourier Transform Infrared Spectrometer which monitors the 8 to 12 micron region of the infrared spectrum. The spectrometer is designated the XM 21. The XM 21 currently uses a narrow band mercury cadmium telluride (MCT) detector. This MCT detector has a number of problems associated with its use in the XM 21. Among these problems are that the detector must operate at 77.degree. K. using liquid nitrogen provided by a Stirling cooler. The Stirling cooler uses 20-30 watts of power. The MCT response curve also drops off sharply when not on the relatively narrow responsivity peak for the detector. In addition the current mean time between failures of the Stirling cooler is only 500 hours.